Solvent refining and dewaxing hydrocarbon oil



June 6, 1939. w. B. HENDREY SOLVENT REFINING AND DEWAXING HYDROCARBON OIL Filed May 1, 1937 WALDERs'EE B HENDREY INVENTOR BY ATTORNEY Patented June 6, 1939 UNITED STATES PATENT OFFICE i SOLVEN T REFINING AND DEWAXING HY- The Texas Company, poration of Delaware New York, N. Y., a cor- Application May 1, 1937, Serial No. 140,083

4 Claims.

This invention relates to solvent refining and dewaxing hydrocarbon oil.

The invention broadly contemplates removing loW viscosity index constituents from wax-bearing lubricating oil by treatment With an extraction solvent highly selective between loW and high viscosity index constituents of the oil and removing the Wax from the oil by treatment with a suitable auxiliary solvent in the presence of the highly selective extraction solvent.

More specically, the invention has toI do with the treatment of residual lubricating oil vstocks in the presence of a diluent, such as propane, with a solvent of the type such as chlorphenol or cresol to remove lo-w viscosity index constituents.

In this treatment, the oil is separated into an extract phase comprising low viscosity index constituents dissolved in the larger proportion of the selective solvent, and a raiiinate phase comprising high viscosity index constituents together With Wax mixed with the remaining portion of the extraction solvent. This raffinate phase also has mixed With it a large portion of' the diluent.

The raffinate phase is dewaxed by employing an auxiliary solvent, such as. chloroform or isopropyl ether, in conjunction with the solvent liquid retained in the rainate phase.

The process of this invention is particularly applicable to the treatment of residual lubricating oil stocks, such as derived from Mid-Continent crude, with a selective solvent comprising a mixture of paraand orthomonochlorphenol and containing around 50 to '75% of parachlorphenol.

It has been found that a chlorphenol mixture, such as this is quite effective in treating residual lubricating oil fractions to produce therefrom raffinate oil of high'viscosity index and having a comparatively light color and a lovv residual carbon content.

Advantageously, the chlorphenol mixture may comprise a distillate obtained by distilling to a temperature up to about 220 C. and at atmospheric pressure a mixture resulting from chlorinating crude phenol under conditions such that at least 60% of the phenol has been chlorinated. The distillate so obtained comprises mainly a mixture of orthoand parachlorphenol, and may contain unreacted phenol together with a small amount of dichlorphenol.

Prior to distillation, the chlorinated mixture may be treated with a small amount` of alkali suilicient to remove hydrogen chloride formed during the chlorination. In this way, a distilled chlorphenol mixture may be obtained having a composition as indicated belovv, and Whichwwill (Cl. 19E- 13) provide a satisfactory selective solvent for the M rening of residual lubricating oil stocks:

Per cent by volume It has been found that a solvent mixture having a composition Within the range above specied is suitable for the purpose of this invention. The relative proportions of orthoand paramonochlorphenol in the mixture can be varied to some extent, but it is desirable that substantial proportions of each of these compounds be present and that the parachlorphenol should predominate.

Thus, in a mixture of paraand orthochlorphenol, the paracompound advantageously constitutes about 50 to 70% thereof by volume.

While this type of selective solvent is particularlyY satisfactory in the refining of residual stocks, it has limited solvent capacity for liquid constituents of lubricating oil at dewaxing temperatures, even though the proportion of solvent r is increased and there is present a diluent solvent such as a liqueed normally gaseous petroleum hydrocarbon. Consequently, Where it is desired to use the chlorphenol solvent in the dewaxing step, I have found it particularly advantageous to employ in conjunction therewith an auxiliary solvent having the so-lvent action of chloroform. Chloroform is miscible With the chlorphenol mixture at dewaxing temperatures of around 0 F. and below, and at the same time exerts solvent action upon those constituents of the oil which do not otherwise remain completely dissolved in the chlorphenol, or in the mixture of chlorphenol and diluent at the dewaxing temperatures.

With chloroform present, the solvent mixture provides a solvent Which at temperatures of 0 F. and below has substantially complete solvent action upon the liquid constituents of the oil and substantially no solvent action upon the Wax or solid hydrocarbon constituents of the oil. solvent mixture is such that, upon chilling to precipitate the wax and removing the Wax so precipitated, the resulting dewaxed oil, after removal of the solvent, will have a pour test temperature substantially the same as the temperature at which the Wax was removed. In other Words, the solvent mixture of my invention permits realizing a substantially z'ero dewaxingtemperature differential. It permits utilizing the The chlorphenol solvent vretainedv in the rafiinate u phase as a component of the dewaxing solvent in the dewaxing step.

Where extraction precedes dewaxing, the waxbearing raiiinate is of highly parainic character. Accordingly, the dewaxing solvent must be of such nature that it will retain the liquid paraflinic constituents completely in solution at the dewaxing temperatures. This requires that the dewaxing solvent be selective as between liquid and solid paraiins at the dewaxing temperature. Consequently, it is necessary to employ a third solvent component in the dewaxing step which will augment the solvent capacity of the retained chlorphenol for the liquid parailinic constituents of the oil.

In order to further illustrate the practice of my invention, reference will now be made to the accompanying drawing showing a flow diagram of the process. A residual lubricating oil fraction, such as derived from Mid-Continent crude, is introduced to the mid-portion of a vertical extraction tower l. This tower is advantageously provided with suitable packing material, such as Raschig rings, adapted to bring about complete contact between the solvent and the oil.

The chlorphenol mixture, such as described above, is introduced to the upper portion of this tower, while a liqueed normally gaseous hydrocarbon, such as propane, is introduced to the lower portion thereof.

In some cases, it may be desirable to mix the propane with the wax-bearing oil prior to introduction to the tower. In any case, countercurrent contact is eected between the oil and chlorphenol mixture so that the formation of extract and raiiinate phases occurs.

The extract phase, containing low viscosity index constituents dissolved in the major portion of the chlorphenol mixture, is withdrawn from the bottom of the tower and subjected to such further disposition as may be desired.

The raffinate phase, comprising high viscosity index oil, some chlorphenol mixture and a large proportion of propane, is removed from the top of the tower and conducted to a mixer 2, wherein it is mixed with an auxiliary solvent comprising chloroform.

The resulting mixture is conducted from the mixer 2 to a chiller 3. This chiller may be the conventional type of chilling equipment wherein the mixture of solvent and oil is brought into indirect heat exchange relationship with a stream of refrigerant liquid. On the other hand, the chiller may be of the evaporative type wherein a portion of the propane contained in the raffinate phase is vaporized from the mixture with refrigerative effect, the propane so vaporized being drawn off through a cooling coil and condenser 4 to a compressor not shown.

The chilled mixture, at a temperature of around 0 to 20 F'. or lower, is conducted to a filter 5 wherein the solid hydrocarbons'are removed in the form of a lter cake of wax. The resulting filtrate is conducted to a still 6 wherein the solvent is removed, leaving a dewaxed oil.

A particular advantage of employing chloroform as the auxiliary solvent is that it has a boiling point of around 6l to 62 C., as compared with a boiling point of 175 to 217 C. for a chlorphenol'mixture. The chloroform can, therefore, be readily separated from the chlorphenol mixture by distillation so that the chlorphenol is thus in a condition for reuse in the extraction tower I.

It is, of course, contemplated that the ratio of solvent to oil used in the extracting and dewaxing steps, and also the temperatures at which these steps are carried out, may be varied, depending upon the type of oil undergoing treatment and also upon the degree of rening action desired. In carrying out the extraction step, for example, the proportion of chlorphenol solvent used may range from one to three parts by volume of solvent to one volume of oil undergoing treatment, while the proportion of propane used may range from one to seven volumes to one volume of oil. Usually in a tower countercurrent operation, from one to two volumes of selective solvent are used, and about three to ve Volumes of propane.

In the dewaxing step, the dewaxing solvent mixture may comprise about one part of chloroform to one-half to one part of chlorphenol, the ratio of solvent mixture to oil being around two to four parts of solvent mixture to one part of oil. Where isopropyl ether is used, instead of chloroform, the isopropyl ether is aboutl 40% to 80% of the mixture of ether and chlorphenol.

It is contemplated that other diluents may be used instead of propane. For example, aromatic hydrocarbons, such as benzol or mixtures of benzol and toluol.

Obviously many modications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of refining residual wax-bearing mineral oil comprising extracting the oil in the presence of a liquefied normally gaseous petroleum hydrocarbon with a monochlorphenol mixture containing around 50 to 75% of parachlorphenol, forrning an extract phase containing low viscosity index constituents dissolved in the solvent liquid and a railinate phase comprising high viscosity index constituents and wax mixed with some of the solvent, separating the phases, adding t'o the rainate phase an auxiliary solvent liquid comprising chloroform in such proportion that the liquefied hydrocarbon, chlorphenol and auxiliary solvent mixture exerts substantially complete selective action as between liquid and solid hydrocarbon constituents of the oil at said temperatures, chilling the mixture to precipitate solid hydrocarbons, and removing the solid hydrocarbons so precipitated.

2. The method of refining residual wax-bearing lubricating oil comprising extracting the oil with a solvent comprising a mixture containing around 0 to 40% phenol, 30 to 55% parachlorphenol, 20 to 50% orthochlorphenol, and 0 to 3% dichlorphenol, forming an extract phase containing low viscosity index constituents dissolved in a portion of the solvent and a rainate phase comprising high viscosity index constituents and mixed with a portion of the solvent, adding to the raflinate phase an auxiliary solvent liquid comprising chloroform in such proportion that the solvent mixture exerts substantially complete selective action as between liquid and solid hydrocarbon constituents of the oil at said temperatures, chilling the mixture to precipitate solid hydrocarbons, and removing the solid hydrocarbons so precipitated.

3. The method of dewaxing residual wax-bearing oil to produce oil having a pour test of 0 F. and below which comprises diluting the oil, mixing therewith a chlorphenol mixture of ortho and parachlorphenol containing around 50 to 75% of containing around 0 to 40% phenol, 30 to 55% parachlorphenol, 20 to 50% orthochlorphenol, and 0 to 3% Vdichlorphenol, and a substantial proportion of an auxiliary solvent liquid comprising chloroform such that the diluent, chlorphenol mixture and auxiliary solvent together have substantially complete selective action as between wax and oil at a temperature of 0 F. and below, chilling the mixture to 0 F. and below to precipitate wax, and removing the wax so 10 precipitated. f WALDERSEE B. HENDREY. 

